Lidar Observations of the PSCs and Stratospheric Aerosols over Eureka in Canadian Arctic

Abstract

The behavior of the polar stratospheric clouds, PSCs, and the stratospheric aerosols is very important to understand the ozone destruction in the polar stratosphere. Lidar observations of the PSCs and stratospheric aerosols have been carried out at the Arctic stratospheric ozone observatory, AStrO, near the Eureka weather station at 80°N, 86°W since February 1993, using a depolarization sensitive NdrYAG lidar. During the four winter campaigns from February 1993 to February 1996, no PSC was observed in the winter of 1992/1993 and 1993/1994, however, several PSC events were observed in the winter of 1994/1995 and 1995/1996. The first event appeared on December 12, 1994 and continued to December 16, 1994. The PSCs in this event are categorized into the TYPE la, which is considered to be crystallized nitric acid trihydrate (NAT) particles. The second event happened from January 5 and 14, 1995, with a short disappeared period on 10 and 11. In the later event, less depolarized component hung down to about 14 km altitude from the main peak, where the TYPE la existed, with higher depolarization around 20 km. The temperature in the hung down region was obviously higher than the freezing point of the NAT. This suggests that the compositions of the PSCs are not only NAT and/or ice but also other species such as sulfuric acid tetrahydrate (SAT) and sulfuric acid dihydrate (SAD) particles.